• Biomedical Science Letters
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• v.11 no.3
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• pp.307-310
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• 2005

Cerebral ischemia results in neuronal changes in remote areas that have fiber connections with the ischemic area. The aim of this study was to investigate the nigral changes by examining the correlation between the apparent diffusion coefficient (ADC) and the tissue structure. Sprague-Dawley rats were subjected to middle cerebral artery occlusion. Four days after the occlusion, when T2-weighted images revealed the presence of an area of high signal intensity in the ipsilateral substantia nigra, and the ADCs were calculated and imaged. Histopathologic examination by both light and electron microscopy was performed on day 4 after surgery. This finding was consistent with the high signal intensity seen on T2-weighted and diffusion-weighted images, as well as with the ADC reduction, but we did not expect to observe uniform ADC reduction attributable mainly to astrocytic swelling in the perivascular end-feet.

• Journal of the Korean Ceramic Society
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• v.48 no.3
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• pp.205-210
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• 2011

The dependence of sulfur redox behavior and its diffusivity on temperature and composition was studied in mixed alkali silicate melts by means of square wave voltammetry (SWV) at different frequencies in a temperature range of $1000^{\circ}C$ to $1400^{\circ}C$. The voltammograms showed two reduction peaks at high frequency but only one peak at low frequency. Irrespective of $K_2O/(Na_2O+K_2O)$, each peak potential due to reduction of $S^{6+}$ to $S^{4+}$ and $S^{4+}$ to $S^0$ moved toward a negative direction with temperature decrease, and the peak current showed a strong dependence on frequency at a constant temperature. However, the compositional dependence of the peak potential showed an inconsistent behavior with an increase of $K_2O$. The mixed alkali effect was not observed in sulfur diffusion. This inconsistency of both peak potential and diffusion for compositional dependence may be derived from the strong volatilization of sulfur in melts.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.333-339
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• 1995

The reduction and diffusion process(R-D process) is an economical way to produce the functional materials which contain rare-earth elements and has been applied to the production of rare-earth magnet meterials($SmCo_5$, $Nd_{15}Fe_{77}B_8$), magneto-optical(MO) target materials and hydrogen storage alloy, etc. However, because of difficult to control of the final composition, the R-D process has not been applied to production of the 2-17 type rare earth permanent magnet materials which contain several elements. Therefore, this work was as a basic study for the production of the 2-17 type rare earth permanent materials with composition $Sm(Co_{0.72}Fe_{0.21}Cu_{0.05}Zr_{0.03})_{7.9}$ by the R-D process, the following were mainy examined ; the amount of metallic calcium as a reductant, homogenization condition of the alloy after the R-D reaction, masuring of magnetic properties of the sample after step aging. The sample prepared by the R-D process contained a little more oxygen than that prepared by the melting method, however, showed almost the same magnetic properties.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.949-955
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• 2000

Numerical study with detailed chemistry has been conducted to investigate the NOx formation and structure in $CH_4/Air-CO_2$ counterflow diffusion flames. The importance of radiation effect is identified and the role of $CO_2$ addition is addressed to thermal and chemical reaction effects, which can be precisely specified through the introduction of an imaginary species. Also NO separation technique is utilized to distinguish the contribution of thermal and prompt NO formation mechanisms. The results are as follows : The radiation effect is dominant at low strain rates and it is intensified by $CO_2$ addition. Thermal effect mainly contributes to the changes in flame structure and the amount of NO formation but the chemical reaction effect also cannot be neglected. It is noted that flame structure is changed considerably due to the addition of $CO_2$ in such a manner that the path of methane oxidation prefers to take $CH_4 {\rightarrow}CH_3{\rightarrow}C_2H_6{\rightarrow}C_2H_5$ instead of $CH_4 {\rightarrow}CH_3{\rightarrow}CH_2{\rightarrow}CH$. At low strain rate(a=10) the reduction of thermal NO is dominant with respect to reduction rate, but that of prompt NO is dominant with respect to total amount.

• Journal of the Korean Institute of Gas
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• v.21 no.2
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• pp.50-57
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• 2017

Shale gas reservoir are composed of very fine grained particles, and their pores are very small, at the scale of nanometers. In this study, a parametric study was implemented to investigate the effect of knudsen diffusion, relative permeability and permeability reduction in shale gas reservoir. Shale gas reservoir model in Horn-River was developed to confirm the productivity for different design parameters such as diffusion, relative permeability, connate water saturation, and permeability reduction.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1187-1188
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• 2006

This paper compares the effect of using different types of iron powders for the preparation of $Sm_2Fe_{17}$ by calciothermic reduction-diffusion (CRD). Three types of iron powder were used: carbonyl, sponge and water atomized. The results show that, when immediately nitrogenated after the CRD process, $Sm_2Fe_{17}$ prepared from sponge and water atomized iron powders yield $Sm_2Fe_{17}N_3$-magnets with a high degree of texture. However, after a suitable treatment with hydrogen followed by nitrogenation, $Sm_2Fe_{17}$-powders made from Carbonyl iron produce magnets with the best quality regarding coercivity, remanence and degree of texture.

• Journal of Welding and Joining
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• v.32 no.5
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• pp.13-20
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• 2014

A brief overview is given of the corrosion and hydrogen diffusion behaviors of high strength pipe steel in sour environment. Firstly, hydrogen adsorption and diffusion mechanism of the pipe steel is introduced. Secondly, the effect of iron sulfide film precipitated as a result of the corrosion reaction on the steel surface on hydrogen reduction reaction and subsequent hydrogen permeation through the steel is discussed. Moreover, the hydrogen diffusion behavior of the pipe steel under tensile stress in both elastic and plastic ranges is reviewed based on a number of experimental permeation data and theoretical models describing the hydrogen diffusion and trapping phenomena in the steel. It is hoped that this paper will result in significant academic contributions in the field of corrosion and hydrogen related problems of the pipe steel used in sour environment.

• Korean Journal of Remote Sensing
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• v.31 no.1
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• pp.21-28
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• 2015

The essential idea of de-noising is referring to neighboring pixels of a center pixel to be updated. Conventional adaptive de-noising filters use local statistics, i.e., mean and variance, of neighboring pixels including the center pixel. The drawback of adaptive de-noising filters is that their performance becomes low when edges are contained in neighboring pixels, while anisotropic diffusion de-noising filters remove adaptively noises and preserve edges considering intensity difference between neighboring pixel and the center pixel. The anisotropic diffusion de-noising filters, however, use only intensity difference between neighboring pixels and the center pixel, i.e., local statistics of neighboring pixels and the center pixel are not considered. We propose a new connectivity function of two adjacent pixels using statistics of neighboring pixels and apply connectivity function to diffusion coefficient. Experimental results using an aerial image corrupted by uniform and Gaussian noises showed that the proposed algorithm removed more efficiently noises than conventional diffusion filter and median filter.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.971-974
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• 2012

The facilitated diffusion effect on protein-DNA binding is studied. A rigorous theoretical approach is presented to deal with the coupling between one-dimensional and three-dimensional diffusive motions. For a simplified model, the present approach can provide numerically exact results, which are confirmed by the lattice-based Monte Carlo simulations.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.910-915
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• 2005

In this study a series of tests(bench scale test) are carried out for increasing in strength of clayey soil by EK-Injection method. In addition, the effects of strength increase in the treated sample are measured by operating the vane shear test device during 25 days at 5 days intervals in order to estimate the effect of ground improvement caused by diffusion. The test results show that the strength increase was developed approximately double to 7 times in comparison to initial shear strength, and outstanding strength increase was created as much as 7 times while injecting the sodium silicate and phosphoric acid in anolyte and catholyte. In addition, the measured shear strength with the influence of diffusion and reduction of water-content had a tendency to converge in constant value in proportion to elapsed time. As a result of this study, strength increment developed by the influence of EK-Injection and diffusion rather than the reduction of water-content were high as 1000% on average